A navigation device is a device that determine its own location information and other parameters in real-time via the American Global Positioning System (GPS). Other similar systems are GLONASS (Russia), and Galileo (Europe). Such navigation device is also referred to as a GPS system, a navigation system, or the like.
Recently, various apparatuses for vehicles using navigation devices have been introduced. These apparatuses may provide only basic audio information for safe driving such as information on frequent accident zones, over-speed zones, and road details.
In the past, GPS navigation devices were prohibitive mainly because of their high costs. Nowadays, however, the costs of GPS navigation devices have reduced substantially, and thus they are frequently installed on many vehicles.
The present invention is derived from studies regarding IT new growth power core technology development business, conducted by the Ministry of Information and Communication and the Institute of Information Technology Association. [Reference No.: 2007-S-301-01, Title: IT Strategic Technology Development]
Most digital clocks, such as a clock installed on a vehicle, are driven by using a cheap crystal oscillator. Since the vibration period of the oscillator is easily influenced by external factors such as electronic noise or heat, a time error increases as time goes by.
The easiest method increasing its stability is to replace the digital clocks with atomic clocks using cesium or rubidium. However, these atomic clocks are very expensive, and thus are not widely used as compared to general digital clocks. Thus, since most of the clocks installed on vehicles at present use a cheap crystal oscillator, the time error increased as time goes by. Accordingly, the users must directly periodically correct time information, and accuracy and precision of users' corrections are limited.